Brainstem gliomas consist of a heterogeneous group which vary greatly in histology and prognosis.
It should be noted that if not otherwise specified the term brainstem glioma usually refers to the most common histology, the diffuse brainstem glioma, and in children is most likely a diffuse midline glioma H3 K27M–mutant.
Brainstem gliomas account for ~25% of all posterior fossa tumours and are most common in children between 7 and 9 years of age 5. There is no recognised gender or racial predilection.
Brainstem gliomas are also recognised in adults, although they are rare accounting for only 2% of adult brain tumours 7. They typically occur in younger adults (third and fourth decade) and tend to be of low grade (WHO I or II) 7.
Although the exact presentation will vary according to location and size of the tumour, in general patients will exhibit a combination of 4:
- cranial nerve palsies
- long tract signs
The duration of symptoms is usually much shorter in diffuse gliomas, in which the history is typically very short (a few days) 4. Additionally, diffuse gliomas more frequently have multiple cranial nerve palsies.
Recognised histological types include:
- diffuse astrocytoma
- usually diffuse midline glioma H3 K27M–mutant (WHO grade IV)
- other tumours also encountered (WHO grades II-IV)
- focal glioma
- (dorsally) exophytic glioma 4,6
- Low-grade astrocytoma
NF1 associated brainstem glioma
- seen in up to 9% of NF1 patients
- most frequently seen in the medulla
- appears similar to a sporadic focal brainstem glioma but has an even better prognosis, with little if any progression
The most frequently used classification system is to divide these tumours into four types 5:
- diffuse brainstem glioma
focal brainstem glioma
- tectal plate glioma
- other focal gliomas
- (dorsally) exophytic
- probably an artificial group made up of the downward extension of true brainstem gliomas or upward extension of upper cervical cord intramedullary spinal cord tumours 5
As a general rule mesencephalic tumours tend to be of a lower grade than those in the pons and medulla 3.
- most common location
- classic location for the childhood 'brainstem glioma' which tends to refer to a diffuse pontine glioma, the majority of which are diffuse midline gliomas, H3 K27M–mutant
- focal dorsally exophytic brainstem glioma is an uncommon variant accounting for only 10% of pontine tumours, and has a much better prognosis, as it usually represents a pilocytic astrocytoma
- overall survival of pontine gliomas is 10% at 5 years
- least common location
- includes focal dorsally exophytic, focal, diffuse and cervicomedullary junction variants
- cervicomedullary junction tumours usually represent upper cervical tumours extending superiorly
- most common location for NF1 associated tumours
MRI is the imaging modality of choice. The appearance will vary with the tumour type, thus please refer to individual articles.
May show anterior displacement of the basilar artery.
Treatment and prognosis
Again, both treatment and prognosis are significantly influenced by tumour type, morphology and location. Radiation is a key part of treatment.
As a general rule, dorsal exophytic tumours and cervicomedullary tumours tend to do best with surgery, whereas surgery has no role in the management of diffuse brainstem gliomas.
- terrible prognosis
- 90-100% patients die within 2 years of diagnosis 6
- focal (tectal glioma)
- excellent long-term survival with CSF shunting (essentially benign lesions)
- focal (other)
- good long-term prognosis with surgery
- (dorsally) exophytic tumours
- good long-term prognosis with surgery
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- 7. Mehta MP. Principles and Practice of Neuro-Oncology, A Multidisciplinary Approach. Demos Medical Pub. (2010) ISBN:1933864788. Read it at Google Books - Find it at Amazon